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Cell death is a key feature of neurological diseases, including stroke and neurodegenerative disorders. Studies in a variety of ischemic/hypoxic mouse models demonstrate that poly(ADP-ribose) polymerase 1 (PARP-1)-dependent cell death, also named PARthanatos, plays a pivotal role in ischemic neuronal cell death and disease progress. PARthanatos has its unique triggers, processors, and executors that convey a highly orchestrated and programmed signaling cascade. In addition to its role in gene transcription, DNA damage repair, and energy homeostasis through PARylation of its various targets, PARP-1 activation in neuron and glia attributes to brain damage following ischemia/reperfusion. Pharmacological inhibition or genetic deletion of PARP-1 reduces infarct volume, eliminates inflammation, and improves recovery of neurological functions in stroke. Here, we reviewed the role of PARP-1 and PARthanatos in stroke and their therapeutic potential.

The excitatory neurotransmitter glutamate shapes learning and memory, but the underlying epigenetic mechanism of glutamate regulation in neuron remains poorly understood. Here, we showed that lysine demethylase KDM6B was expressed in excitatory neurons and declined in hippocampus with age. Conditional knockout of KDM6B in excitatory neurons reduced spine density, synaptic vesicle number and synaptic activity, and impaired learning and memory without obvious effect on brain morphology in mice. Mechanistically, KDM6B upregulated vesicular glutamate transporter 1 and 2 (VGLUT1/2) in neurons through demethylating H3K27me3 at their promoters. Tau interacted and recruited KDM6B to the promoters of Slc17a7 and Slc17a6, leading to a decrease in local H3K27me3 levels and induction of VGLUT1/2 expression in neurons, which could be prevented by loss of Tau. Ectopic expression of KDM6B, VGLUT1, or VGLUT2 restored spine density and synaptic activity in KDM6B-deficient cortical neurons. Collectively, these findings unravel a fundamental mechanism underlying epigenetic regulation of synaptic plasticity and cognition.

Background Apoptosis-inducing factor (AIF), as a mitochondrial flavoprotein, plays a fundamental role in mitochondrial bioenergetics that is critical for cell survival and also mediates caspase-independent cell death once it is released from mitochondria and translocated to the nucleus under ischemic stroke or neurodegenerative diseases. Although alternative splicing regulation of AIF has been implicated, it remains unknown which AIF splicing isoform will be induced under pathological conditions and how it impacts mitochondrial functions and neurodegeneration in adult brain. Methods AIF splicing induction in brain was determined by multiple approaches including 5′ RACE, Sanger sequencing, splicing-specific PCR assay and bottom-up proteomic analysis. The role of AIF splicing in mitochondria and neurodegeneration was determined by its biochemical properties, cell death analysis, morphological and functional alterations and animal behavior. Three animal models, including loss-of-function harlequin model, gain-of-function AIF3 knockin model and conditional inducible AIF splicing model established using either Cre-loxp recombination or CRISPR/Cas9 techniques, were applied to explore underlying mechanisms of AIF splicing-induced neurodegeneration. Results We identified a nature splicing AIF isoform lacking exons 2 and 3 named as AIF3. AIF3 was undetectable under physiological conditions but its expression was increased in mouse and human postmortem brain after stroke. AIF3 splicing in mouse brain caused enlarged ventricles and severe neurodegeneration in the forebrain regions. These AIF3 splicing mice died 2–4 months after birth. AIF3 splicing-triggered neurodegeneration involves both mitochondrial dysfunction and AIF3 nuclear translocation. We showed that AIF3 inhibited NADH oxidase activity, ATP production, oxygen consumption, and mitochondrial biogenesis. In addition, expression of AIF3 significantly increased chromatin condensation and nuclear shrinkage leading to neuronal cell death. However, loss-of-AIF alone in harlequin or gain-of-AIF3 alone in AIF3 knockin mice did not cause robust neurodegeneration as that observed in AIF3 splicing mice. Conclusions We identified AIF3 as a disease-inducible isoform and established AIF3 splicing mouse model. The molecular mechanism underlying AIF3 splicing-induced neurodegeneration involves mitochondrial dysfunction and AIF3 nuclear translocation resulting from the synergistic effect of loss-of-AIF and gain-of-AIF3. Our study provides a valuable tool to understand the role of AIF3 splicing in brain and a potential therapeutic target to prevent/delay the progress of neurodegenerative diseases.

Traumatic brain injury (TBI), often induced by sports, car accidents, falls, or other daily occurrences, is a primary non-genetically related risk factor for the development of subsequent neurodegeneration and neuronal cell death. However, the molecular mechanisms underlying neurodegeneration, cell death, and neurobehavioral dysfunction following TBI remain unclear. Here, we found that poly(ADP-ribose) polymerase-1 (PARP-1) was hyperactivated following TBI and its inhibition reduced TBI-induced brain injury. Macrophage migration inhibitory factor (MIF), a newly identified nuclease involved in PARP-1-dependent cell death, was translocated from the cytosol to the nucleus in cortical neurons following TBI and promoted neuronal cell death in vivo. Genetic deletion of MIF protected neurons from TBI-induced dendritic spine loss, morphological complexity degeneration, and subsequent neuronal cell death in mice. Moreover, MIF knockout reduced the brain injury volume and improved long-term animal behavioral rehabilitation. These neuroprotective effects in MIF knockout mice were reversed by the expression of wild-type MIF but not nuclease-deficient MIF mutant. In contrast, genetic deletion of MIF did not alter TBI-induced neuroinflammation. These findings reveal that MIF mediates TBI-induced neurodegeneration, neuronal cell death and neurobehavioral dysfunction through its nuclease activity, but not its pro-inflammatory role. Targeting MIF's nuclease activity may offer a novel strategy to protect neurons from TBI.

Additional file 2: Supplementary Figure 2. Expression of AIF3 in neurons in vitro and mouse cortex under different pathological conditions. Supplementary Figure 3. Characterization of neuron marker expression in the cortex of AIF3 splicing mice at P30.

Additional file 1: Supplementary Figure 1. Identification of AIF3 isoform.

Galanin (GAL) plays key role in many pathophysiological processes, but its role in ischemic stroke remains unclear. Here, the models of 1 h middle cerebral artery occlusion (MCAO)/1-7 d reperfusion (R)-induced ischemic stroke and in vitro cell ischemia of 1 h oxygen-glucose deprivation (OGD)/24 h reoxygenation in primary cultured cortical neurons were used to explore GAL's effects and its underlying mechanisms. The results showed significant increases of GAL protein levels in the peri-infarct region (P) and infarct core (I) within 48 h R of MCAO mice (p

Interleukin (IL)-17A was reported to be involved in the development of post-ischemic stroke inflammatory response and functional recovery. However, the IL-17A dynamic changes in serum/cerebrospinal fluid (CSF) and its role in neuronal injury following ischemic stroke are unclear.In vivo ischemic stroke was induced by 1 h of middle cerebral artery occlusion (MCAO) and 6 h-7 d reperfusion (R) in mice, while in vitro stroke was induced by 1 h oxygen-glucose deprivation (OGD)/24 h reoxygenation (R) in cultured cortical neurons. Enzyme-linked immunosorbent assay (ELISA) and double-labeled immunofluorescence of IL-17A with neuron (NeuN), astrocyte (GFAP) and microglia (Iba-1)-specific markers were used to determine the IL-17A levels in serum/CSF and neural cell type.The ELISA results showed that IL-17A significantly increased both in peri-infarct region (p 0.001) and CSF (p 0.05) following 1 h MCAO/R 12 h. The levels of IL-17A in serum increased at R 1 d (p 0.05) and peaked at R 3 d (p 0.001) after 1 h MCAO. Immunofluorescent staining demonstrated that IL-17A co-localized with GFAP in peri-infarct regions. In addition, recombinant rIL-17A could aggravate ischemic injuries at dose-dependent manner in 1 h OGD/R 24 h-treated neurons companying with the increase of IL-17A receptor il-17RA mRNA (p 0.001) and IL-17R protein levels.We firstly reported astrocytic IL-17A peaks in CSF within 12 h and in serum at 3 d reperfusion after ischemic stroke. IL-17A may exaggerate neuronal injuries through its receptor IL-17R at early stage of ischemic stroke.

Conventional protein kinase C (cPKC)γ participated in cerebral hypoxic preconditioning-induced neuroprotection and affected the neurological outcome of ischemic stroked mice. As an independent predictor of ischemic stroke, the internal carotid artery occlusion (ICAO)-caused brain-regional ischemic injury may worsen the neurological outcome of patients. However, the brain-regional ischemic vulnerability and its underlying mechanism remain unclear. In this study, the bilateral ICAO (BICAO) model was applied in cPKCγ wild type (WT) and knockout (KO) mice to determine the cPKCγ impact on brain-regional ischemic vulnerability. The arterial spin labeling (ASL) imaging results showed that 7 days BICAO-induced global ischemia could cause significant blood perfusion loss in prefrontal cortex (69.13%), striatum (61.69%), hypothalamus (67.36%), hippocampus (69.82%) and midbrain (40.53%) of WT mice, along with neurological deficits. Nissl staining and Western blot results indicated that hypothalamus and midbrain had more severe neural cell loss than prefrontal cortex, striatum and hippocampus, which negatively coincided with endogenous cPKCγ protein levels but not blood perfusion loss and cPKCγ membrane translocation levels. Furthermore, we found that cPKCγ KO significantly aggravated the neuron loss in prefrontal cortex, striatum and hippocampus and abolish the regional ischemic vulnerability by using immunofluorescent staining with neuron-specific marker NeuN. Similarly, cPKCγ KO also significantly increased Caspase-3, -8 and -9 cleavage levels in prefrontal cortex, striatum, hippocampus, hypothalamus and midbrain of mice with 24 h BICAO. These results suggested that hypothalamus and midbrain are more vulnerable to ischemia, and endogenous cPKCγ affects the regional ischemic vulnerability through modulating Caspase-8 and -9 dependent cell apoptosis.

We have reported that neuron-specific conventional protein kinase C (cPKC)γ is involved in the development of cerebral hypoxic preconditioning (HPC) and the neuroprotection against ischemic injuries, but its molecular mechanism is unclear. In this study, the adult and postnatal 24 h C57BL/6J wild-type (cPKCγ+/+) and cPKCγ knockout (cPKCγ−/−) mice were respectively used to establish the models of middle cerebral artery occlusion (MCAO)-induced ischemic stroke in vivo and oxygen-glucose deprivation (OGD)-treated primarily cultured cortical neurons as cell ischemia in vitro. The results showed that cPKCγ knockout could increase the infarct volume and neuronal cell loss in the peri-infarct region, and enhance the neurological deficits, the impaired coordination, and the reduced muscle strength of mice following 1 h MCAO/1–7 days reperfusion. Meanwhile, cPKCγ knockout significantly increased the conversion of LC3-I to LC3-II and beclin-1 protein expression, and resulted in more reductions in P-Akt, P-mTOR, and P-S6 phosphorylation levels in the peri-infarct region of mice with ischemic stroke. The autophagy inhibitor BafA1 could enhance or reduce neuronal cell loss in the peri-infarct region of cPKCγ+/+ and cPKCγ−/− mice after ischemic stroke. In addition, cPKCγ knockout and restoration could aggravate or alleviate OGD-induced neuronal ischemic injury in vitro through Akt-mTOR pathway-mediated autophagy. These results suggested that cPKCγ-modulated neuron-specific autophagy improves the neurological outcome of mice following ischemic stroke through the Akt-mTOR pathway, providing a potential therapeutic target for ischemic stroke.